In an advanced long-term evolution (LTE-advanced) system, in order to increase throughput of a cell-edge user, much attention is paid to a coordinated multiple point (CoMP) transmission technology.
FIG. 1 is a schematic diagram of a CoMP transmission scenario within a same cell based on remote radio heads (RRHs), and FIG. 2 is a schematic diagram of a CoMP transmission scenario within different cells based on RRHs. It can be seen from FIGS. 1 and 2 that different transmission points within the same cell may perform coordinated transmission, and different transmission points within the different cells may also perform coordinated transmission.
In CoMP transmission, in order to select an optimal set of coordinated points, a base station side needs to obtain information on downlink channels from each transmission point to a user. In order to obtain information on downlink channels from each transmission point to a user, following method may be used: user equipment transmits a sounding reference symbol (SRS), and each point of the base station side receives the SRS at the same time, uplink channels from the user equipment to each receiving point is calculated at the base station side, and hence information on downlink channels from each transmission point to the user equipment is calculated.
However, in the implementation of the present invention, the inventors found that following defect exists: in order to support multiple pieces of user equipment transmits SRSs at the same time, different frequency domain resources may be occupied, for example, different subbands may be occupied, or different frequency combs may be occupied, or different codeword resources, such as cyclic shift (CS), may be occupied. However, in an existing system, at most 2 frequency combs and 8 CSs may be supported. When different transmission points within the same cell perform CoMP transmission, capacity of an SRS is limited as increase of the number of users and multipoint reception of the SRS, and gain of downlink CoMP transmission will be affected. There is no effective solution for the above problem.
It should be noted that the above description of the background art is merely provided for clear and complete explanation of the present invention and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background art of the present invention.